Zeolites are crystalline aluminosilicate molecular sieves which have a microporous three-dimensional framework structure. In general, the crystalline zeolites are formed from corner-sharing AlO.sub.2 and SiO.sub.2 tetrahedra and are characterized by having pore openings of uniform dimensions, having a significant ion-exchange capacity, and being capable of reversibly desorbing an adsorbed phase which is dispersed throughout the internal voids of the crystal, without significantly displacing any atoms which make up the permanent crystal structure.
Zeolite beta, which is described in U.S. Pat. No. RE 28,341 and is incorporated by reference, is one particular zeolite which has recently received considerable attention for catalyzing various types of reactions. Zeolite beta is usually synthesized in a basic medium in the presence of tetraethylammonium and alkali cations and has a Si/Al mole ratio from about 5 to about 100. A molecular sieve with the zeolite beta structure but containing titanium in the framework is described in Spanish patent no. 2,037,596 which also discloses that the titanium containing material can be used as a catalyst in selective oxidation reactions of organic compounds using hydrogen peroxide, organic peroxides or hydroperoxides as the oxidizing agent.
WO97/33830 discloses the synthesis of zeolite beta using fluoride anions as the mineralizing agent at or near neutral pH. It is disclosed that these materials exhibit enhanced thermal stability and low concentration of SiO or SiOH defects over a wide chemical composition range. Finally, T. Blasco et al. in J. Phys. Chem. B, 1998, 102, p. 75 disclose the incorporation of titanium into the beta structure by using the procedure in WO97/33830 again over a wide Si/Al range. These materials also have increased hydrophobicity.
There is also a number of reports where tin has been incorporated into the framework. U.S. Pat. No. 5,648,558 discloses a metallo-aluminosilicate having a skeletal structure of zeolite beta and having substituted in the aluminosilicate a metal species such as chromium, gallium, boron, tin, etc. Aluminum is always present in these molecular sieves. In U.S. Pat. No. 4,543,347 it is stated that compositions containing SiO.sub.4 and MO.sub.4 tetrahedra are known in the art. Tin is included in a list of 21 elements but no reference is given which provides synthesis conditions. In U.S. Pat. No. 5,399,336 a stannozeosilite is disclosed which has the MFI structure. U.S. Pat. No. 5,110,571 discloses stannosilicates in which tin is octahedrally coordinated and have diffraction patterns of other than that of zeolite beta. U.S. Pat. No. 4,933,161 discloses substituting Sn into an aluminosilicate zeolite. Some aluminum is always present. In U.S. Pat. No. 4,576,805 a process for increasing the total amount of lattice metal in a porous inorganic oxide is disclosed. The composition is represented by the formula: (1-x)SiO.sub.2 :(x)MO.sub.n/2 where M is at least one lattice metal selected from Groups IIIB, IVB, VB, VIB, VIIB, VIII, IIIA, IVA and VA. Although tin is one of the metals included in the list, again no reference or method is provided to prepare the initial porous oxide. U.S. Pat. No. 4,329,328 discloses a method of preparing zinco/stanno/titano-silicate with the structure of zeolite A, X and Y. U.S. Pat. No. 5,401,488 discloses a molecular sieve with an empirical formula of (Sn.sub.w Al.sub.x Si.sub.y)O.sub.2. Aluminum is always present in the formula. WO 88/01254 discloses a process for modifying the framework of a zeolite by replacing aluminum in the framework by elements such as tin. Finally, N. K. Mal and A. V. Ramaswanvy in Chem. Commun., pp. 425-426, 1977, discloses the synthesis of an alumina free tin containing zeolite beta.
In contrast to this art, applicants have synthesized a series of molecular sieves having SnO.sub.2 and SiO.sub.2 tetrahedral oxide units and at least one of TiO.sub.2 or GeO.sub.2 tetrahedral oxide units and have an empirical formula of: EQU (Sn.sub.x TI.sub.y Si.sub.1-x-y-z Ge.sub.z)O.sub.2
where "x", "y" and "z" are the mole fractions of tin, titanium and germanium.
These metallo-stannosilicate molecular sieves are useful as catalysts in selective oxidation processes such as olefin epoxidation and hydroxylation of aromatic compounds.